American hotels all down the east coast of the continental USA and the Canadian ones I stayed in in Toronto and Grande Prairie, Alberta all have those twist-to-lock bolts, but *also* have a hinged metal device that replaces the old-fashioned chain. It is often difficult to engage because it has been installed with tight clearances but once snagged over the ball-ended spike on the door it will prevent the door opening more than an inch or so.
To break in past one of these you could either force the door to break the latch off, or you could cut through it with a cutting wheel or sawzall. A correctly proportioned pry-bar could also be used to deform the latch until it snapped I suppose.
None of these options would qualify as "just walking in unannounced" in my book.
Now I've never been to Las Vegas, so I don't know if their hotel room doors are fitted with what seems to this traveler to be a ubiquitous standard in the industry, but if they don't, why would anyone "hip" to security concerns stay there?
You are right that there is security theater here. I'm becoming more convinced by the minute that there were actors chewing the scenery on both sides of the check in desk.